Two-year intermittent exposure of a multiwalled carbon nanotube by intratracheal instillation induces lung tumors and pleural mesotheliomas in F344 rats.

BACKGROUND: A mounting number of studies have been documenting the carcinogenic potential of multiwalled carbon nanotubes (MWCNTs); however, only a few studies have evaluated the pulmonary carcinogenicity of MWCNTs in vivo. A 2-year inhalation study demonstrated that MWNT-7, a widely used MWCNT, was a pulmonary carcinogen in rats. In another 2-year study, rats administered MWNT-7 by intratracheal instillation at the beginning of the experimental period developed pleural mesotheliomas but not lung tumors. To obtain data more comparable with rats exposed to MWNT-7 by inhalation, we administered MWNT-7 to F344 rats by intratracheal instillation once every 4-weeks over the course of 2 years at 0, 0.125, and 0.5 mg/kg body weight, allowing lung burdens of MWNT-7 to increase over the entire experimental period, similar to the inhalation study. RESULTS: Absolute and relative lung weights were significantly elevated in both MWNT-7-treated groups. Dose- and time-dependent toxic effects in the lung and pleura, such as inflammatory, fibrotic, and hyperplastic lesions, were found in both treated groups. The incidences of lung carcinomas, lung adenomas, and pleural mesotheliomas were significantly increased in the high-dose group compared with the control group. The pleural mesotheliomas developed mainly at the mediastinum. No MWNT-7-related neoplastic lesions were noted in the other organs. Cytological and biochemical parameters of the bronchoalveolar lavage fluid (BALF) were elevated in both treated groups. The lung burden of MWNT-7 was dose- and time-dependent, and at the terminal necropsy, the average value was 0.9 and 3.6 mg/lung in the low-dose and high-dose groups, respectively. The number of fibers in the pleural cavity was also dose- and time-dependent. CONCLUSIONS: Repeated administration of MWNT-7 by intratracheal instillation over the 2 years indicates that MWNT-7 is carcinogenic to both the lung and pleura of rats, which differs from the results of the 2 carcinogenicity tests by inhalation or intratracheal instillation.

Iron oxide nanoparticles exert inhibitory effects on N-Bis(2-hydroxypropyl)nitrosamine (DHPN)-induced lung tumorigenesis in rats.

Iron oxide nanoparticles (magnetite) have been widely used in industry and medicine. However, the safety assessment of magnetite has not been fully completed. The present study was conducted to assess effects of magnetite on carcinogenic activity, using a medium-term bioassay protocol. A total of 100 male Fischer 344 rats, 6 weeks old, were randomly divided into 5 groups of 20 animals each, and given a basal diet and drinking water containing 0 or 0.1% of N-bis(2-hydroxypropyl)nitrosamine (DHPN) for 2 weeks. Two weeks later, the rats were intratracheally instilled magnetite 7 times at an interval of 4 weeks, at the doses of 0, 1.0 or 5.0 mg/kg body weight, and sacrificed at the end of the experimental period of 30 weeks. The multiplicities of macroscopic lung nodules and histopathologically diagnosed bronchiolo-alveolar hyperplasia, induced by DHPN, were both significantly decreased by the high dose of magnetite. The expression of minichromosome maintenance (MCM) protein 7 in non-tumoral alveolar epithelial cells, and the number of CD163-positive macrophages in tumor nodules were both significantly reduced by magnetite. It is suggested that magnetite exerts inhibitory effects against DHPN-induced lung tumorigenesis, by the reduction of alveolar epithelial proliferation and the M2 polarization of tumor-associated macrophages.

A case of spontaneous Zymbal's gland carcinoma with lung metastasis in an aged Fischer 344 rat.

Zymbal's gland neoplasms are induced in rats through the administration of various carcinogens, but spontaneous neoplasia is rare. This report describes a spontaneous Zymbal's gland carcinoma with lung metastasis found in an aged male Fischer 344 rat. Macroscopically, the dome-like tumor nodule, approximately 30 mm in diameter with ulceration, was located near the ear canal of the rat. No healthy tissue or structure of Zymbal's gland was identified on the corresponding side, while the normal salivary glands and a lacrimal gland were observed. Histologically, a large part of the tumor mass was occupied by poorly differentiated neoplastic cells, the shapes of which were oval to polygonal or fusiform. Additionally, clusters of sebaceous-like foamy cells and squamous metaplasia with prominent keratinization were observed. Tumor cells were found to metastasize to the lung; these cells displayed histological similarities, including a sebaceous gland-like pattern, to those in the primary site. The tumor cells were immunohistochemically positive for cytokeratin AE1/AE3 or vimentin but negative for CD68, S100, α-smooth muscle actin, von Willebrand factor, and desmin. Our results indicate that the tumor was a poorly differentiated Zymbal's gland carcinoma with lung metastasis.

A histopathological analysis of spontaneous neoplastic and non-neoplastic lesions in aged male RccHan:WIST rats.

Histopathological information about spontaneous lesions in aged Hannover Wistar rats is limited. In this study, we describe spontaneous lesions found in 39 male RccHan:WIST rats used as a control in a carcinogenicity study. Neoplastic lesions were frequently seen in the endocrine system, such as pituitary adenomas in the pars distalis. This strain exhibited a high incidence of thymoma (10.3%), compared to other strains. We encountered an oligodendroglioma, a pituitary adenoma of the pars intermedia, and a prostate adenocarcinoma, which are comparatively rare in rats. While the variety and incidence of non-neoplastic lesions were similar to those in other strains, several interesting lesions occurred with relatively high incidence, including "harderianization" of the extraorbital lacrimal gland, common bile duct ectasia, and hyperplasia of pulmonary endocrine cells in the lung. Furthermore, comparative analyses demonstrated that the severity of chronic progressive nephropathy and murine progressive cardiomyopathy in RccHan:WIST rats was less than that in F344 rats.

Cytotoxic effects of psychotropic benzofuran derivatives, N-methyl-5-(2-aminopropyl)benzofuran and its N-demethylated derivative, on isolated rat hepatocytes.

The novel psychoactive compounds derived from amphetamine have been illegally abused as recreational drugs, some of which are known to be hepatotoxic in humans and experimental animals. The cytotoxic effects and mechanisms of 5-(2-aminopropyl)benzofuran (5-APB) and N-methyl-5-(2-aminopropyl)benzofuran (5-MAPB), both of which are benzofuran analogues of amphetamine, and 3,4-methylenedioxy-N-methamphetamine (MDMA) were studied in freshly isolated rat hepatocytes. 5-MAPB caused not only concentration-dependent (0-4.0 mm) and time-dependent (0-3 h) cell death accompanied by the depletion of cellular ATP and reduced glutathione and protein thiol levels, but also accumulation of oxidized glutathione. Of the other analogues examined at a concentration of 4 mm, 5-MAPB/5-APB-induced cytotoxicity with the production of reactive oxygen species and loss of mitochondrial membrane potential was greater than that induced by MDMA. In isolated rat liver mitochondria, the benzofurans resulted in a greater increase in the rate of state 4 oxygen consumption than did MDMA, with a decrease in the rate of state 3 oxygen consumption. Furthermore, the benzofurans caused more of a rapid mitochondrial swelling dependent on the mitochondrial permeability transition than MDMA. 5-MAPB at a weakly toxic level (1 mm) was metabolized slowly: levels of 5-MAPB and 5-APB were approximately 0.9 mm and 50 µm, respectively, after 3 h incubation. Taken collectively, these results indicate that mitochondria are target organelles for the benzofuran analogues and MDMA, which elicit cytotoxicity through mitochondrial failure, and the onset of cytotoxicity may depend on the initial and/or residual concentrations of 5-MAPB rather than on those of its metabolite 5-APB. Copyright © 2016 John Wiley & Sons, Ltd.

Long-term Pulmonary Responses to Quadweekly Intermittent Intratracheal Spray Instillations of Magnetite (Fe3O4) Nanoparticles for 52 Weeks in Fischer 344 Rats.

Information about potential risks of iron nanomaterials is still limited, while a wide variety of applications are expected. We recently reported acute phase responses of male and female Fischer 344 rats after a single intratracheal spray instillation of Fe3O4 nanoparticles (magnetite), clearly showing dose-dependent pulmonary inflammatory changes (Tada et al., J Toxicol Pathol 25, 233-239, 2012). The present study assessed long-term responses of male and female Fischer 344 rats to multiple administrations of magnetite. Ten-week-old male and female Fischer 344 rats (n=20/group) were exposed to a total of 13 quadweekly intermittent intratracheal spray instillations of magnetite during the experimental period of 52 weeks, at doses of 0, 0.2 (low), 1.0 (medium) and 5.0 (high-dose) mg/kg body weight per administration. Absolute and relative lung weights of the high-dose group were significantly higher than those of the control group. Macroscopically, slight enlargement and scattered black patches were recognized in the lungs and the lung-associated lymph nodes of the high-dose group. Histopathologically, infiltration of macrophages phagocytosing magnetite (all dose groups) and of chronic inflammatory cells (medium- and high-dose males and high-dose females), alveolar bronchiolization and granuloma (high-dose group) were observed. In addition, alveolar hyperplasias were observed in some rats of the high-dose group, and cytoplasmic overexpression of ß-catenin protein was immunohistochemically found in such lesions. The present results clearly show that instilled magnetite causes chronic inflammatory responses in the lung. These responses occur in a dose-dependent manner without apparent differences among sexes.

Hepatic and renal toxicities and metabolism of fentanyl analogues in rats.

New synthetic opioids continue to emerge in the illicit market, and among them, fentanyl analogues pose a serious threat to the public health with their abuse and trafficking. We investigated the toxicity of fentanyl analogues on the liver and kidneys mediated by the µ-opioid receptor (MOR). Our study focused on 4-fluoro-isobutyrylfentanyl (4F-iBF), which is classified as a "narcotic" in Japan; structurally similar analogues 4-chloro-isobutyrylfentanyl (4Cl-iBF) and isobutyrylfentanyl (iBF) were also investigated. Rats that were intraperitoneally administered 4F-iBF (5 mg/kg (12.3 µmol/kg)) or iBF (12.3 µmol/kg) displayed hepatic and renal ischemic-like damage, but 4Cl-iBF (12.3 µmol/kg) did milder renal damage only. We found that the agonist activity of 4F-iBF, at MORs was approximately 7.2 times that of 4Cl-iBF, and that pretreatment with MOR antagonist naltrexone (0.8 mg/kg) alleviated liver and kidney injuries caused by 4F-iBF. These results suggested that 4F-iBF might cause ischemic damage to the liver and kidneys, induced by respiratory depression mediated by MORs. Furthermore, to elucidate the metabolism of fentanyl analogues, we investigated the change over time in the amount of 4F-iBF, 4Cl-iBF, iBF (6.15 µmol/kg, respectively), and their respective metabolites in serum after intraperitoneal administration to rats. The results showed that in 24-h post-dose serum, 4Cl-iBF and iBF were substantially eliminated while 4F-iBF remained at about 30% of the maximum level, and each of the N-dephenylethylated metabolites of 4F-iBF, 4Cl-iBF, and iBF was detected in 2-h post-dose serum. The results from this study revealed information on the hepatic and renal toxicities and metabolism related to fentanyl analogues.

Acute phase pulmonary responses to a single intratracheal spray instillation of magnetite (fe(3)o(4)) nanoparticles in Fischer 344 rats.

Iron nanomaterials are of considerable interest for application to nanotechnology-related fields including environmental catalysis, biomedical imaging, drug delivery and hyperthermia, because of their superparamagnetic characteristics and high catalytic abilities. However, information about potential risks of iron nanomaterials is limited. The present study assessed pulmonary responses to a single intratracheal spray instillation of triiron tetraoxide nanoparticles (magnetite) in rats. Ten-week-old male and female Fischer 344 rats (n=5/group) were exposed to a single intratracheal spray instillation of 0 (vehicle), 5.0, 15.0 or 45.0 mg/kg body weight (BW) of magnetite. After 14 days, the rats were sacrificed, and biological consequences were investigated. The lung weights of the 15.0 and 45.0 mg/kg BW male and female groups were significantly higher than those of the control groups. The lungs of treated rats showed enlargement and black patches originating from the color of magnetite. The typical histopathological changes in the lungs of the treated rats included infiltration of macrophages phagocytosing magnetite, inflammatory cell infiltration, granuloma formation and an increase of goblet cells in the bronchial epithelium. The results clearly show that instilled magnetite causes foreign body inflammatory and granulating lesions in the lung. These pulmonary responses occur in a dose-dependent manner in association with the increase in lung weight.

Reproductive and neurobehavioral effects of maternal exposure to dinotefuran in the F1 -generation mice.

BACKGROUND: Few studies were found on the neurobehavioral toxicity of dinotefuran in mammals. This study was designed to evaluate the reproductive and neurobehavioral effects of maternal exposure to dinotefuran in mice. METHODS: Dinotefuran was given in the diet at levels of 0% (control), 0.012% (18.2-50.6 mg/kg body weight [bw]/day), 0.03% (44.2-125.8 mg/kg bw/day), and 0.075% (111.3-311.0 mg/kg bw/day) in females (10/group) during the gestation (gestation day 1-5 to 15-19) and lactation periods (lactation day 0 to 24-28). Selected reproductive and neurobehavioral parameters were measured in the F1 generation. RESULTS: Litter size and litter weight significantly increased in the high-dose group. The average body weight of male and female offspring increased in treatment groups at postnatal day (PND) 21. In female offspring, surface righting on PND 4 was delayed in higher-dose groups. Cliff avoidance on PND 7 was delayed in a dose-related trend. The route of olfactory orientation on PND 14 was delayed in the high-dose group. For exploratory behavior of the F1 generation, the frequencies of mice with urination increased in a dose-related trend in male offspring. In female offspring, the related variables of rearing increased in dose-related manners. The average rearing time lengthened and the number of defecations increased in the high-dose group in adult males. In adult females, the rearing time shortened in the high-dose group. Several variables differed in the high-dose group for spontaneous behavior in adult females. CONCLUSIONS: The dose levels of dinotefuran produced several adverse effects on neurobehavioral parameters in mice.

Flame retardant tetrabromobisphenol A induced hepatic changes in ICR male mice.

Tetrabromobisphenol A (TBBPA) is widely used throughout the world as flame retardant for electronic equipment or building materials, and is detected in air at the dismantling plant, sewage sludge, sediment or human serum samples. In the present study, we examined the effects of TBBPA on the liver when administered to mice for 14 consecutive days. Groups of 7 (control group) or 8 (treated group) Crlj:CD1 (ICR) male mice were given 0 (control), 350, 700 or 1400mg/kg body weight/day TBBPA (99.1% pure) in olive oil for 14 days. The serum concentration of total-cholesterol in high-dose (1400mg/kg BW) group was higher than those of the control group. Absolute and relative liver weights were dose-dependently increased, and were significantly increased in high-dose (1400mg/kg BW) group. The histological findings showed that the slight enlargement of the hepatocytes, inflammatory cell infiltrations and focal necrosis of hepatocytes were more marked in liver of treated groups (from 350mg/kg BW) than in control group. The present data suggest the possibility of inducing hepatic lesion by TBBPA dosing.